Disk drives are apparatus comprising one or more substantially thin, magnetic disks that are rotated by a spindle motor that is responsive to the drive's control mechanism and associated electronics that communicate data via read and write heads. The disk drives are used in computer systems, such as personal computers, laptop computers and workstation equipped with computer systems, to store large amounts of data, (giga-byte range), in a form that is machine readable for subsequent use by a user. The magnetic disk comprises a surface of magnetizable material having a number of annular regions, called tracks, that extend circumferentially around the disk. Each track is divided into blocks called sectors. Data and other identification information is stored in the sectors in the form of magnetic transitions. The reading and writing of data is accomplished by read and write heads and are positioned over the required track by the drive's positioning control system. The system typically includes the use of solenoid type voice coil actuators for high resolution. The quantity of data that can be stored on a disk depends upon how much of the surface area is magnetized for the storage of a bit. Ideally, use of the entire disk surface for writing data is a desirable objective. However, the ideal objective is not yet possible. Traditionally, the data tracks are written at a fixed nominal spacing based on a particular drives's design point that is determined by the disk's area density required to meet the drive's data storage byte capacity point. The disk's data recording surface has been traditionally allocated to include: an outer guard band, a data zone, and an inner guard band. The physical act of placing the head over the required track for performing the read and write operations is not done with 100% accuracy. The drive crash stop tolerances are very large and impact the reliability of the drive. The head positioning dilemma has been traditionally resolved by including extra tracks in the disk's inner guard band, essentially widening the landing zone, see FIG. 1. By example, a 1.35 gigabyte disk drive may have a minimum track spacing that results in a nominal track design of 5100 tracks for all 1.35 gigabyte drives. From this nominal design information, each disk would be allocated an outer guard band having 84 tracks, a data zone having 4923 tracks and a landing zone of 93 tracks, see FIG. 2. From this design information, a corresponding nominal track width of 196 micro-inches would impact a 170 micro-inch wide write head as shown in FIG. 3. If a disk is determined to have extra spacing for additional tracks, the extra tracks would be allocated to the inner guard band. The disk's data real estate is sacrificed to improve reliability, rather than risk having too few tracks in the inner guard band and allow the read/write heads to land on data. The extra tracks on the disk go unused by the drive, which effectively results in decreasing the drive's read, write and servo margins and further results in a higher than needed tracks per inch. To applicant's knowledge, a method for determining and optimizing a disk's tracks per inch spacing which defines the disk area that can be used for writing data on a disk has not been taught by the prior art. To applicant's knowledge, the prior art has used a predetermined bounded distance for determining the number of tracks per inch available for writing data, even though the disk may have extra tracks which could be used for storing data.
Thus, a need is seen to exist for a disk drive having a data storage disk adapted with optimized tracks per inch spacing that is facilitated by a method for determining a disk's area and associated radial distance that can be used for writing data and establishing from the determined radial distance the disk's actual tracks per inch (tpi) spacing that can be used for writing data and using the determined tracks spacing on that disk for writing data.
It is therefore a primary object of the present invention to provide a disk drive having a data storage magnetic disk adapted with optimized tracks per inch spacing that is facilitated by a method that includes determining the disk's spacing and associated radial distance that can be used for writing data and establishing from the determined radial distance the disk's actual tracks per inch (tpi) spacing, or track width, that can be used for writing data and using the determined track width on that disk for storing data.